The present invention relates, in a general way, to headlights with a discharge lamp.
Normally such a headlight comprises a reflector in which is mounted a discharge lamp, supplied with power by a separate high-voltage power-supply module, fixed, for example, in or onto the casing of the headlight. A screened cable links the power-supply module to the lamp, while the electromagnetic emissions in the region of the lamp and of its power-supply module are trapped by specific screening arrangements.
Discharge lamps have recently been developed characterized by having all or part of the high-voltage power-supply circuit present in a fixed or removable base of the lamp. Recourse is thus avoided to a power-supply casing housing the converter and high-voltage circuits, and therefore heavy and bulky, and difficult to place in a motor-vehicle headlight the requirements of which in terms of compactness and of lightness are constantly increasing. Hence, with this type of lamp, only one DCxe2x80x94DC converter circuit has to be provided separately from the lamp, with a substantially reduced weight and bulk.
One difficulty which can be expected with this new type of lamp, however, lies in the problems of electromagnetic compatibility as regards the power-supply circuits associated with the lamp.
Hence, in order to improve the electromagnetic compatibility all round the headlight, it may prove to be necessary to design the adjoining bodywork of the vehicle in such a way that it participates in the screening with respect to the stray electromagnetic emissions.
It will be understood that this will constitute an undesirable constraint on the constructors, given that they wish to preserve complete freedom in the design of the bodywork at the front of the vehicle. Such an approach is inapplicable, moreover, in the case of bodywork made of composite materials, or more generally non-conducting materials.
The present invention aims to overcome these problems of the prior art, and to propose a headlight which, in itself, without increasing the weight, complexity or cost price either of its casing or of other elements, and without having to design the adjacent bodywork in a specific way as regards these questions of interference, is able to satisfy the usual requirements in terms of electromagnetic compatibility.
To that end, according to a first aspect, it proposes a motor-vehicle headlight, comprising a gas-discharge lamp combined with a power-supply circuit and mounted in a mirror, and means of screening with respect to interfering electromagnetic emissions, characterized in that the said power-supply circuit is accommodated in a housing associated with the lamp to the rear thereof, and in that the screening means comprise a conducting material entirely surrounding the said housing and able to provide electrical continuity between a screening braid of a power-supply cable arriving at the said housing and screening arrangements which are associated with the mirror.
Preferred, but non-limiting, aspects of the headlight according to the invention are as follows:
the said conducting material belongs to a casing defining the said housing,
the said conducting material is mechanically fixed to the outside of the said casing,
the said conducting material is deposited on an outer face of the said casing,
the said conducting material belongs to a cover affixed to the rear of the mirror and surrounding a non-conducting casing defining the said housing,
the headlight comprises first linking means for ensuring electrical continuity between the said conducting material surrounding the said housing and a second, screening, conducting material provided at the rear surface of the mirror,
the first linking means comprise a series of clips electrically linked to the said second conducting material and bearing against the said first conducting material,
the said clips are mounted on a lamp holder affixed to the mirror,
the first linking means comprise arrangements for supporting the said cover against the said second conducting material at the rear of the mirror,
the first linking means comprise a deformable seal made of electrically conducting material, interposed between the first and second conducting materials,
the deformable seal is mounted on the mirror,
the deformable seal is mounted on a lamp holder affixed to the mirror,
the headlight comprises second linking means for ensuring electrical continuity between the said conducting material surrounding the said housing and the said screening braid,
the casing of the lamp possesses a first connector, the end of the power-supply cable possesses a second connector able to plug into the first connector, and, when the first and second connectors are separated, the said second linking means are able to break the electrical continuity between the said conducting material surrounding the said housing and the said screening braid only after the contacts of the first and second connectors carrying the power-supply voltage for the lamp have been separated,
the second linking means comprise a series of clips carried by the said second connector, the said clips being in contact with the screening braid and with the conducting material surrounding the casing,
the said second linking means comprise a conducting seal in contact with the screening braid and with the conducting material surrounding the casing,
an elastic means is provided for retaining the lamp in axial position, the said means bearing against the conducting, screening material, and the said elastic means, which is conducting and which, in retaining position, is in contact with the said screening braid of the cable, forms part of the said second linking means,
the said second linking means comprise arrangements for support against the braid of the power-supply cable, which are formed on the said cover around an orifice for the said cable to pass,
the headlight comprises a conducting elastic element able to bear against the said conducting material in the region of a rear face of the said casing, in order simultaneously to retain the lamp in axial direction and to provide electrical continuity for screening with other screening elements of the headlight,
the said housing forms an integral part of the lamp,
the said housing forms part of a connector on which the lamp is mounted removably,
the headlight further comprises control circuits accommodated in an electrically conducting control box situated at a distance from the lamp, and third linking means for ensuring electrical continuity between the said control box and the braid of the cable,
the third linking means comprise a third connector provided on the control box and a fourth connector provided at the end of the power-supply cable opposite to the lamp and able to be plugged into the third connector, and, when the third and fourth connectors are separated, the said third linking means are able to break the electrical continuity between the said control box and the said screening braid only after the contacts of the third and fourth connectors carrying the power-supply voltage for the lamp have been separated.
According to a second aspect, the present invention proposes a gas-discharge lamp for a motor-vehicle headlight, the said lamp being combined with a power-supply circuit, characterized in that it incorporates the said power-supply circuit in a housing, and in that it further comprises screening means comprising a conducting material entirely surrounding the said housing and able to ensure electrical continuity between a screening braid of a power-supply cable arriving in the housing and screening arrangements provided on a mirror able to accommodate the said lamp.